Stylus-Drag..Fact or Fiction?

Halcro. Thanks for posting the videos. I have seen tests like this before and the thing which startles is how quickly the platter slows down. All due to the drag induced by a tiny diamond thrashing about in a plastic groove. Others have said that a high moment of  inertia platter will save the day. Don't know what the inertia figure for the Raven is but the platter itself does look substantial, so it is reasonable to assume that it isn't a feather weight. 
A  high inertia platter simply changes the time constant for a given motor torque. Sure, its deceleration rate will be slower but it will also take longer to recover. There doesn't seem to be any free lunch here.
Also agree totally with atmasphere. "a robust drive" is a common thread through most of the collectable vintage TTs  

Wouldn't setting the speed with the arm lowered be, at best, a compromise?
What record do you choose? Surely the stylus drag is modulation dependant, so if you choose to set the speed at a 'medium modulation' level record, the platter will run fast some of the time and slow some of the time. This, purely dependant on what is going on with the music. Add in the radius where you lowered the arm and it becomes a lottery. 

While coreless motors exhibit no cogging, they do show, at a much lower level, perturbations in output torque. As designed and as built are two different things. 

Is this audible? maybe. What this wonderful hobby has taught me is that pretty much everything is audible, at least in the analogue world where I live.   

Mike.
Exactly. This is what I was trying to say with respect to dynamic speed stability, (steadiness)
The level of granularity we use to measure TTs is simply too crude to show us what is going on in real time under dynamic conditions.  

But we sure can hear it.

chakster.

I said... "I don't claim to be able to hear this difference"

You seem to be agreeing with me?.

Raul raises a good point. How accurately are the various cutting lathes spinning? This is a whole different topic. 

It does lead nicely into long term average speed accuracy....
There is a trend to show how incredibly accurate peoples DD TTs run, posting videos using the timeline over extended runs. This is a great demonstration of how accurately a TT's long term speed control can be.

But how important is an average 33.3333333 rpm?
Lets say TT1 runs at an average 33.333 and TT2 runs at an average 33.334. A 1000hz tone cut accurately at 33.333 would of course be played back at 1000hz on TT1, but it would be higher on TT2 at 1000.03hz.
I don't claim to be able to hear this difference. 

What I think is important is the TTs dynamic speed accuracy. How does it behave under a varying load. I believe that we are sensitive to real time changes in pitch. But do not hear them as such. Halcro describes the Raven as being more relaxed than the Victor. This general description pretty much covers many BD/DD comparisons. Clearly we are hearing differences but not describing these in terms of pitch. We  use different descriptors.. 

The timeline only tells us how long it takes for the platter to make one rotation. Confirming, or not, that it took 1.8 seconds at its 33.33 setting. That is, was its average speed 33.33 or not.  It does not tell us anything about what happened to the platters dynamic speed during that rotation. 

Yeah, yeah, the platters inertia will save you, I don't think so. There are no free lunches.  


Chris.

Many thanks for the input of which I completely concur.


Lewm
I couldn't resist!  

Hi phoenixengr. why do you think  VPI use trapezoidal commutation?
Surely this is not optimum if they want to minimize torque ripple. 


Cheers

Hi  phoenixengr. VPI have made interesting choices in the controller and motor. You would think that Thingap would make a motor with low speed/power windings ( higher resistance  ) making for finer speed control from the Elmo.
All that said, the TT gets great press, so the package seems to work very well indeed.